Communication networks are used to transport a variety of signals such as voice, video, data transmission, and the like. Traditional communication networks use copper wires in cables for transporting information and data. However, copper cables have drawbacks because they are large, heavy, and can only transmit a relatively limited amount of data. Consequently, optical waveguide cables replaced most of the copper cables in long-haul communication network links, thereby providing greater bandwidth capacity for long-haul links. However, most communication networks use copper cables for distribution and/or drop links on the subscriber side of the central office. In other words, subscribers have a limited amount of available bandwidth due to the constraints of copper cables in the communication network. Stated another way, the copper cables are a bottleneck that inhibit the subscriber from utilizing the relatively high-bandwidth capacity of the long-hauls links.
As optical waveguides are deployed deeper into communication networks, subscribers will have access to increased bandwidth. But there are certain obstacles that make it challenging and/or expensive to route optical waveguides/optical cables deeper into the communication network, i.e., closer to the subscriber. Long-haul applications used fiber optic cable designs typically having relatively large diameters that were robust and thus very stiff for protecting and preserving optical performance in the outdoor environment. These designs worked well for the long-haul application but are not suitable for subscriber applications. Laying the last mile of optical fiber to the subscriber requires a low-cost fiber optic cable that is craft-friendly for installation and connectorization, flexible for slack storage, has a small cross-section, performs well in a cable clamp, and that is versatile. Moreover, the reliability and robustness of the fiber optic cable or protective casings for subscriber applications must withstand the rigors of the outdoor environment such as ice and wind loading without experiencing elevated levels of optical attenuation.
FIG. 1 schematically illustrates two different methods for routing fiber optic cables to a premises 19. Specifically, FIG. 1 shows a first method of routing a fiber optic cable 10 to premises 19 in an aerial application and a second method using a cable 10′ routed to premises 19 in a buried application. In a typical aerial application, cable 10 has a first end 10a that is attached at a first interface device 12 located on pole 11 and a second end 10b that is routed to an interface device 14 at premises 19. In aerial applications, fiber optic cable 10 is attached to the pole and/or house using a clamp device such as a P-clamp holds the cable and allows tensioning of the same. In buried applications, the first and second ends of cable 10′ are respectively routed to pedestal 18 and connected to interface device 16 and routed and connected to interface device 14.
Fiber optic cables have used rigid strength members made of materials such as steel or glass reinforced plactics (grp) that provide tensile strength, allow for clamping, and aid in inhibiting buckling and shrinkage of the cable providing good performance. However, these rigid strength members make the fiber optic cable relatively stiff, thereby inhibiting characteristics such as slack storage and craft-friendliness. In other words, the rigid strength members increase the bending radius of the cable when coiled, and the strength members act like a coiled spring that wants to unwind. Fiber optic cables also have used strength members such as conventional fiberglass yarns or aramid fibers, these strength members provide tensile strength and result in a flexible cable, but generally speaking do not provide anti-buckling strength for the cable. Additionally, conventional fiberglass yarns or aramid fibers do not provide enough coupling to the cable for adequate clamping performance. By way of example, aramid fiber strength members are able to migrate within the clamp relative to the jacket so that forces can be transferred to the optical fibers causing high levels of optical attenuation and in extreme cases can cause the optical fiber to be pulled-out from the optical connector. Consequently, cable designs using conventional fiberglass yarns or strength members are not suitable for the rigors of outdoor drop cable applications since the temperature variations and/or clamping arrangements cause elevated levels of attenuation or cable failure, which are unacceptable. Thus, the prior art cables do not meet all of the requirements for a drop cable that is suitable for routing optical waveguides to the subscriber.